9/21/2007 @ 4:00PM

Bill Vs. Slim

It’s been an intriguing year for wealth watching. Since we released our list of The World’s Billionaires six months ago, declaring Bill Gates the world’s richest man, Mexican telephone mogul Carlos Slim Helú has closed the gap.

Who’s richer now? It depends on what day it is. On Aug. 31, the day we locked in stock prices for this issue’s Forbes 400, Slim and Gates were each hovering at around $59 billion. They were within $500 million of each other–a virtual tie. When dealing with fortunes that big, we cannot be confident that our valuations are closer than $500 million to the mark. Moreover, a move of $2 in the share price for
Microsoft
or a big cell phone company in which Slim holds a 30% stake can add or subtract a billion dollars.

Gates’ overall fortune cannot be reasonably compiled on a daily basis, while Slim’s can. More than half of Gates’ wealth is held in his private investment company, Cascade, which invests in private entities as well as publicly traded stocks and bonds. To know Cascade’s value on a given day is impossible; it takes months of cultivating sources to generate an estimate for its value right before we go to press.

No question, though, that Slim is making a serious case for the title. His fortune has swelled 20% since March, while Gates’ is up only 5%. But as this battle has no bearing on The Forbes 400, which tracks only Americans, we’ll let the markets settle this dispute. Maybe in March there will be a definitive answer.